1. Field of the Invention
The present invention relates to a semiconductor laser apparatus, and more particularly, to a semiconductor laser apparatus where a semiconductor laser device and a beam receiving device for monitoring an output of the semiconductor laser device are provided on the same lead.
2. Description of the Prior Art
In recent years, a great number of improvements have been made in the semiconductor laser apparatus. Of the improvements, a semiconductor laser apparatus shown in Japanese Patent Application No. H4-132513 by the present Applicants is shown in FIG. 1. In the figure, a beam receiving device 42 is placed on a lead 41, and a semiconductor laser device 43 is placed on the lead 41 and in front of the beam receiving device 42. Fine metallic wires are arranged between the beam receiving device 42 and another lead 45 and between the semiconductor laser device 43 and another lead 46, respectively. An insulating frame 44 is formed to partly surround the leads 41, 45 and 46. In the apparatus, an optical part 47 (e.g. a diffraction grating, a half mirror, and an objective lens) for which an accurate position relationship is required with an irradiated beam is normally arranged in front of the semiconductor laser device 43, that is, on the side toward which a main laser beam is irradiated (main irradiation direction). The optical part 47 is fixed onto a circuit board 48, and the lead 41 and the other leads 45 and 46 of the semiconductor laser apparatus are soldered onto the circuit board 48. In this semiconductor laser apparatus, however, it is difficult to solder the leads 41 and the other leads 45 and 46 onto the circuit board 48 since they are close to the optical part 47. Further, since the position of the semiconductor apparatus readily shifts at the time of the soldering, the position relationship between the irradiated beam and the optical part is not accurately held.
In laser beam printers and laser facsimile apparatuses, in order to increase the printing speed, two-beam irradiating semiconductor laser apparatuses have been used. Of such apparatuses, a semiconductor laser apparatus disclosed in Sanyo Technical Review Vol. 20 No. 1, published in February, 1988 is shown in FIG. 2. In FIG. 2, a heat sink 52 and a beam receiving device 53 are placed on a stem 51, and an optical guide 54 and a semiconductor laser device 55 are placed on the beam receiving device 53. The semiconductor laser device 55, which is electrically separated by a groove formed at the center of a monolithic substrate, is provided with a first beam emitting portion 56 and a second beam emitting portion 57 to upwardly emit two beams.
In order to accurately control the intensity of each beam, it is required that the beam from the rear portions of the first and second beam emitting portions 56 and 57 are provided through beam leading paths to beam receiving surfaces 58 and 59 without leaking and overlapping with each other.
In the above-described semiconductor laser apparatus, however, the cost is high for the following reasons: first, the yield is low since the two beam emitting portions 56 and 57 are formed on the monolithic semiconductor laser device 55; second, the cost of the optical guide 54 made of an insulator and having the beam leading paths for leading the beams from the semiconductor laser device 55 is high; and third, the cost of the beam receiving devices 53 having the two beam receiving surfaces 58 and 59 at positions corresponding to the beam leading paths is high, and it makes the manufacture difficult that the positioning of these parts requires much time. For these reasons, this two-beam semiconductor laser apparatus costs ten times as much as the one-beam type and therefore is not practical.